Variable condenser



Oct. 13, 1925. 1,557,316

G. H. Nolnas` VARIABLE CONDENSER Filed Dec. 16, 1924 Patented Oct. 13,1925.

UNITED STATES GEORGE H. NOBBS, OF WATERTOWN, MASSACHUSETTS.

VARIABLE CONDENSER.

Application nled December 16, 1924. Serial No. 756,222.

To all whom zt may concern Be it known that I, GEORGE H. Nons, a citizenof the United States, and resident of Watertown, in the county ofMiddlesex and State of Massachusetts, have invented an Improvement inVariable Condensers, of which the following is a s ecification.

This invention relates to t at class of electrical variable capacitycondensers of the plate type, which are widely used in radio receivingsets and which generally comprise two sets 0r groups of parallel,semicircular plates, one group, called the stator, being stationary, andthe other, called the rotor, being mounted for rotation to permitinterposition of its plates with the stationary plates to a varyingextent, thereby to vary the capacity of the apparatus.

It is Well known that, to secure satisfactory results in a radioreceiving set, a balance, which is as nearly perfect as possible, mustbe secured between the inductance and capacity of the receivingcircuits. Variation of the inductance is usually secured by means of thetaps which are placed in contact with one or more turns of wire on theinductance coil, but the variation secured by cutting in or out of evena single turn of the coil is so great that accurate adjustment of theinductance to the capacity of the circuit in this manner is ordinarilyimpossible. The adjustment of the capacity to the inductance is usuallysecured by means of a condenser of the type above referred to, but evenwhere the inductance has been adjusted to established conditions asclosely as possible by means of the taps, yet inductance is likely tovary to such an extent under different conditions, that it is usuallyditlicult to determine, without making numerous tests, what range ofcapacity will be necessary to secure the desired balance.

Condensers of the type referred to are now made to secure widely varyingranges of capacity between a minimum, which is usually nearly the same,and the maximum which is required, this variation being usually securedby varying the number, size and proximity of the plates. At presentdealers carry condensers in five or more different sizes, designed togive a corresponding number of stages of maximum capacity. In manyinstances it is necessary to make tests with several condensers havin rdifferent maximum capacities, before it 1s ascertained what particularcondenser will give the most satisfactory result under the conditions athand.

The principal reason for the necessity or desirability of usingcondensers having'different degrees of maximum capacity for differentconditions is as follows :-The whole range of capacity of any givencondenser of the above type is secured by turning the rotor through 180.If a condenser of sufficient maximum capacity for all conditions isemployed, the result will be that the correct tuning positions of therotor for certain stations which are broadcasting within certainrelatively low limits of wave length, requiring capacities much lessthan the maximum, will be crowded into a relatively small portion of itstotal range of adjustment, so that the extent of adjustment of the rotornecessary to tune to these stations of relatively low wave length willbe so slight that the different adjustments will practically coincide,thereby making it impossible to tune out one station in favor ofanother. On the other hand, if the range of capacity of the condenser isso reduced that the rotor must be adjusted throughout its entire rangeof movement to adjust the capacity to all of these stations ofrelatively low wave length, the extent of adjustment from one' positionto another to secure the correct tuning therefor will be greatlyincreased, thereby correspondingly increasing the selectivity of thereceiving set for these stations, and making it possible to tune instations which could not be tuned in if the maximum capacity Vof thecondenser was substantially greater.

It has been attempted to obviate the necessity of making tests withcondensers of different maximum capacity to secure desired results byproviding a condenser having several groups of plates, one or more ofwhich may or may not be employed according to conditions, and, whilesuch an apparatus, to some extent, obviates the difficulty, yet the stepup from one maximum capacity to the next is so great with such anarrangement that it is still impossible to adjust the rotor so as tosecure the desired degree of selectivity as to certain stationsrequiring intermediate degrees of capacity.

The objects of my invention are to provide a condenser of the type abovereferred to, having means whereby its maximum capacity may be readilyincreased by small steps or stages from a fixed minimum capacity to anymaximum capacity which is ikely to bek required, the numbersfof stagesof increase in maximum capacity of the condenser to be in directproportion to its greatest possible .range of capacity, so.that

a correspondingly large number of `ranges a,con enservof the type aboveidentiiiedv with means whereby any one Kor more of the stator vplates:may be.readily placed in or ren'li'oved fromi thei condenser circuit,inde .@Jldently, as circumstances may require.

or a more complete understandlng of my inventionure-,ference is `made tothe accompanyingudrawingLfornng a .parti of this specifcafiom in w ich:

Fig. 1 is :a nyiewof an electrical condenser. einv ying a Ipreferredform I,of my invention.

yis a sectional ,View atline 2-2 pf 1. ig.i 3 isY an end zvieW vthereof.

Fig.4 is sectional view at,1ine 4 5-4 of Fig. l'on an enlarged scale.

Fig-.35 is a sectional view, atline 5-5 of Fig,r 1 Vonen, enlargedscale. f

ig6 is a detailE view of portion .of .one of the stator plates .anditsvconnecting device.

As'shown in themdrawing-I providela main ,framewhich' consists of a pairof end platesylOand `12, of electrical insulating material, whicharefconnected by a series of bolts. 14v having clamp' g nuts 15 ,and 16at 'each end, the nuts 1 Y,being ada tedcto be connected to theinstrument pane in the usual r:mannen The -usual l semifcircular,

ectvrically connected toa shaft 20, which is,rotatablyA mounted iin the!end plates 10 and 12and, in' practice, willbe provided witha handle.infrontpf the panel for convenient manipulation.` VA s ring contact 22is provided fortherearfen of the shaft 20to Whichone lterminal, of thecircuit, is,,connected.` Thel stator platesf24, which are similar inthickness and spacing to the rotor plates, are,mounted in parallelismthereto on the bolts. 14, said plates 24 bein ,electrically ,insulatedfroml .said bolts byf g ass ybushingst and from 'each other byinterposed, 1nsulating, s acing Washers 26,I washers or bushings 2 ofrlsor'nevvhat greater thicknessfor len li than the washers i latina-Srscess 36Ysiee spaced rotor plates 18- are mounted on, and. e

` will be my i a,

26, bein provided between ,the re r, stator plateau 'tle rearend au 10,a thi end plates, stator plates an washers being all clamped firmlytogether by means of the nuts on boltshlh 'Ill'esrran ment of the 'i0stator Vplates is such that w en the rotor plates are rot-ated they willbe interposed y bet\veen,thestatorpltes without actually A coming incontact therewith, as is usual ing this class of devices. Itis tobeiunderstood'g'l in this connection that thenumber of y and rotorplates shown ;is 1:nerelyV illustrasf,` tive and that.-, in factice, the.number einen ployed .will,.,be,sucent to'givetbef :narici` mum capacity-1ikelyf,to.be requiredfundarrgso all co-nditOD6;of use." A

A metal rod 28 is muntednthe .back plates 10 and 12 adiacentione1of-,the tiem rods 14,.,and is held; inpgsitioabynut 1 threadedthereon and clamped ain'st- @5 plates. The rear end portlono said rod,is preferably used .asabindingrpost andq has .a .thumb nut 30 thereon.for connecti t the other.circuit terminal 31 thereto. series of switchlevels, 32 are pivotally. mounted uon said rod 28.. in electricalioon.tact therewith and vvitlijeach,.othelysairl.n levers4 being spaced apartby, non-insulati washers 34 and held inrclose Contact wit eachqother, by,a coileiprigthe alifj` nm ement 'being .auch .thatach Alever #mom helthat is,sw1ngs. .inthe, ane of a spend" stator plate 24.. oh lever32",i8i1i provid with a contaet-faeeBB atione ,andli which is madesnghnymanica um axisjoo aboutwhic hf it swings, and is so arranged; that itmay be swuugil linto. .wedging engagfljj meut with the lcorrespondingstatonlatefinf, 1 the'planeof which `Vit swings. Fort e pulii l i poseof incneasingthe arc'cr area of ,nou-.10 tact between lthalevers. andlates,.-eacli{` ,plateale it;` refembh/.prowid with is f f h ig.,6,irtggwihich theocmii aoeO L e, correspon everswmgs' ,t 1;; shapelof the.reeess .being,fsueh that,.whgn f}1 thelevervis pushed, ntoasrm engagnent; as bpossi with the late, the. evergamLE-j; plate wf iba; engathroughout practiqfrl, cally` the entire .bottom surface off the k A`stop 10d, 38 may, be proyidedio limit. l0 opcningfmswinging,movement.,ofthe `lejfe i. In adj the ,device to 'any ,particular set of conditions,itfwilLfrst be decided agg proximateiy how many stator plateswi11 ,Y irequired to secure themaximum capacity" i necessaryfor suchconditiensfand then a oor-,ff responding number of the switch levers.32?, swung into operative relation. withf the corresponding plates, sothat electrinxiid V connect-ion will be established between Suehf platesand the terminal attached f4) le'lodjf 28. .The rotor will then fromthe;` minimum ca acit position of 'g'.'2 to s e-fj i cure, if possile, ecorrect balance with th l. i inductanoe in the usual manner. If the'maxi-"f mum capacity is found to be too high then one or more of thelevers will be restored to its vertical position, or, if it is found tobe too low, then one or more additional plates will be placed in thecircuit by moving the corresponding switch levers 32 to their engagingpositions, as will be obvious. As all the stator plates are insulatedfrom each other, and are only electrically connected to each other andto the terminal 3l through their corresponding switch levers 32, itfollows that the plates not connected will, for the time being at least,be merely dead metal, but as it has been conclusively proven that thepresence of tlie dead plates does not appreciably eii'ect the eiciencyof the receiving set, this fact is not objectionable. The variation inmaximum capacity secured by cutting in or cutting out a single plate isso small that a very accurate adJustment of the maximum capacity desiredmay be secured, so that any one of a large series of ranges of capacityfrom the minimum may be brought in by a semi-revolution ol the iotor inal single condenser constructed as above described.

It will be apparent that, under all ordinary conditions of use, asubstantial number of stator plates will always be employed, so that,under such conditions the connect-ion between such plates and theirterminal might be of a more permanent form than through the switchlevers. However, so far as my invention is concerned it will be apparentthat it is immaterial whether the disconnectable plates are used inconnection with permanently connected plates or not.

l/Vhile I have shown the most satisfactory means of which I am atpresent aware for cutting the stator lates in and out of action, yet itwill be un erstood that other satisfactory means for lthe purpose may beemployed which are Within the scope of my invention.

I claim:

1. An electrical condenser comprising a group of stator plates and agroup of rot-or plates arranged to be moved between said stator platesto vary the capacity, a terminal for each group of plates, the terminalfor the rot-or plates being electrically conneet-ed thereto, means forsupporting said stator plates out of electrical contact with each otherand the terminal thereof and a series of switches corresponding innumber to the stator plates and movable independently of each other toestablish electrical connection between the respective stator plates andtheir terminal.

2. An electrical condenser comprising a group of stator plates and agroup of rotor plates arranged to be moved between said plates out ofelectrical contact with each f other and the terminal thereof and alseries of switch levers electrically connected to the stator terminaland arranged to be swung separately from an inactive position intoengagement with a corresponding stator plate to establish an electricalconnection with its terminal.

3. An electrical condenser comprising a series ot stator plates and aseries of rotor plates arranged in parallelism therewith for variableinterposition with the stator plates to vary the capacity, means forsupporting said stator plates out ot electrica-l contact with cachother, a series ot switch levers, each mounted to swing in the plane ofone of said stator plates and having a contact face arranged to beengaged with the edge thereof to make electrical connection therewithwhen the lever is swung from a disengaged to an engaging position and apair of electrical terminals one being connected to the rotor plates andthe other to said switch levers.

4. Au electrical condenser comprising a series ot stator plates and aseries of rotor plates arranged in parallelism therewith for variableiuterposition with the stator plates to vary the capacity, means forsupporting said stator plates out of electrical cont-act with eachother, a. pivot rod having a series of switch levers each mounted onsaid rod in electrical Contact therewith to swing in the plane ot one ofsaid stator plates and having a contact face arranged to be engaged withthe edge of its corresponding stator plate to make electrical contacttherewith and a pair of terminals one electrically connected to saidrotor plates and the other to said pivot rod.

5. An electrical condenser comprising a series of stator plates and a.series of rotor plates arranged in parallelism therewith tor variableinterposition with the stator plates to vary the capacity, means forsupporting said stator plates out of electrical contact with each other,a series ot switch levers, each mounted to swing in the plane of one ofsaid stator plates and having a cam. face arranged to be swung intowedging engagement with the edge of its corresponding stator plate tomake electrical contact therewith, and a pair of terminals electricallyconnected respectively, one tol said rotor plates and one to said switchlevers.

In testimony whereof, I have signed my name to this specification.

GEORGE H. NOBBS,

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